1. Field of the Invention
The present invention relates to a semiconductor memory device and a method of driving a semiconductor memory device.
2. Background Art
FBC (Floating Body Cell) memory is remarked as a semiconductor memory device in place of DRAM. FBC memory stores data “1” or “0” by accumulating holes in a body region or releasing holes therefrom. FBC memory is more advantageous in microminiaturization than 1T-1C (1 Transistor-1 Capacitor) type DRAM.
However, to keep the state of retaining holes in the body region (the state of data “1”), it is necessary to keep the gate electrode in a large negative potential. Therefore, an intensive electric field is applied between the junction of the body region and the source/drain layer in the reverse-bias direction. This electric field has a function of accumulating holes in the body region in the state not to retain holes (the state of data “0”). There occurs the problem of data retention, namely, deterioration of the capability of retaining data “0” (see U.S. Pat. No. 6,621,725).